The ecological impacts of battery electric vehicles
Electric vehicles are a growing segment of the transportation sector. Either because of government mandate or sheer market-based demand, electric vehicles are expected to be larger players of the existing fleet of automobiles. They are growing rapidly but still have a long way to go: they had a 40% year-on-year increase in 2019, to account for 2.6% of global sales and 1% of global stock (IEA). Most of the new and existing cars are battery electric vehicles, henceforth BEV, automobiles that transform electric energy to mechanical energy via electrochemical energy stored in rechargeable batteries. Because of the efficiency of electric motors relative to combustion engines and the lack of fossil fuels in their operations, BEVs are perceived as a key technology for sustainability. In reality, their effects on the environment are significant.
Electric vehicles are not a novel technology. Some earlier pilots were developed in the earlier 19th century, with Robert Anderson, a Scottish inventor, being credited for the first crude electric carriage in 1832. Nicolaus Otto, a German engineer, came up with the first modern internal combustion engine (ICE) running on petroleum that lead to the compressed charge motors that are dominant nowadays in 1876. The automobile industry was born out of a long series of inventions and trials, with most of them being manufactured in Germany and France in the late 19th century. By the first years of the 20th century, several vehicle options were available: electric, steam-powered or petroleum powered. In the US, electric vehicles reached their peak on those days with about a third of the fleet. No automobile was a clear winner because they all had different tradeoffs: electric vehicles were pollutant free at the tailpipe and quiet, but heavy with low mileage and slow to charge; petroleum vehicles had longer ranges and were quick to start-up but were noisy, dirty and easy to brake; steam vehicles accelerated smoothly but had issues starting up quickly, limits for storing large amounts of fuel and at a higher peril of explosion.
It was until the invention of Ford’s Model T which made ICE petroleum cars the dominant force in the 20th century to our days. The mass manufacturing and performance made these automobiles widely available in the US, who became the world’s powerhouse for manufacturing vehicles on the earlier days. Today, the world produces near 70 million automobiles annually with an existing fleet of more than 1 billion units. In 2010, there was a stock of only 10,000 electric cars globally. Fast forward 10 years later, the number is now 7.2 million. Through government subsidies and both public and private sponsored development, BEV managed to be manufactured at large. Perceived by the policymakers and consumers as a “clean” vehicle, BEV manufacturers often promote them as a solution to prevent global warming and protect our environment. Electric vehicles are indeed more efficient than ICEs, and do not have tailpipe or noise pollutants.
Even though electric motors are more efficient than combustion engines at converting energy to work, the reason they lost the race to petroleum-fueled cars is physics and chemistry. Electric vehicles need to be powered by electricity, which means that they are limited by the availability to get it. The purpose of personal vehicles is to provide flexibility and convenience. Hence, if mobility is restricted by the limitations of access to electricity, a mode of transportation with easier way to store energy is more competitive. Batteries are heavier and bigger per unit energy compared to petroleum and other fuels. For that reason, they provide lower range compared to a petroleum car of the same size. Moreover, they are slower to recharge.
Crude oil has generally a density of 45.5 MJ/kg in terms of mass, and 38.5 MJ/l in terms of volume. The batteries used in Tesla’s BEV have a density of 0.88 MJ/kg and 2.56 MJ/l. Considering this, plus the losses of conversion of energy to electricity, the improved efficiency of electric motors relative to combustion engines dissipates. Fossil fuels are degrees of magnitude more energy dense than batteries even considering the useful energy disadvantage, which can be neglected considering the efficiency losses of generating electricity too. While batteries have been getting better over time and faster than expected, they are reaching their physicochemical limits. The competitiveness of batteries as a carrier of energy is limited by the architecture of the devices plus the chemical and physical properties of the elements used. In order to make batteries with higher energy density, new battery chemistries need to be discovered and commercialized.
The majority of the batteries used in BEV today are liquid state lithium-ion batteries. Such batteries were discovered and researched in the late 70’s and early 80’s, commercialized in the early 90’s but reached their most advanced state in the 2010’s. Quantumscape, a manufacturer of solid-state batteries for electric cars, recently announced a breakthrough using solid-state lithium-ion batteries. The higher bound density of such batteries is 1.8 MJ/kg, still lower by a factor of more than 20 relative to oil. A promising technology is lithium-air batteries, where oxygen is used as a catode and the theoretical specific energy is equal to 41.9 MJ/kg. However, this type of battery is still in its infancy and requires massive amounts of research to overcome many challenges to be a reality, let alone marketable and manufactured at scale. The median timeline from invention to commercialization in the energy technology sector is 30 years. Hence, we can expect that for a couple of decades the majority of BEV will be using the current state-of-the-art lithium-ion batteries.
Many countries or local jurisdictions have stated intentions on banning combustion engines vehicles in favor of electric vehicles in the 2030's, while many car manufacturers have announced going fully electric in the same timespan. It is unlikely electric vehicles meet the intended growth to dominate the market despite their current rapid expansions due to scale and availability of raw materials. The International Energy Agency (IEA) estimates that the fleet of electric vehicles needs to grow 30-fold today’s levels to meet the goals of the Paris Agreement. However, on their current policies scenarios, light BEVs are expected to reach a stock of 89.4 million. This implies a 10-fold increase of today’s levels, but certainly more plausible.
The sustainability purpose of BEVs is to mitigate greenhouse gases, but their manufacturing has embodied emissions that take thousands of kilometers of driving to offset relative to fossil-fuel powered ICEs conditional on charging over periods with lower grid emissions. But even under no operational emissions under a low-carbon electricity grid, BEVs still emit carbon in their lifetime because of their production and disposal. And the embodied emissions in their manufacturing come from higher embodied energy, which means that there are many other upstream impacts. The main problem arises from the battery, whose production is energy intensive and includes the extraction and processing of metals and minerals with high toxicity and ecological footprint. Moreover, they are posed to keep piling on the massive e-waste problem, of which less than 18% is recycled globally.
The ecological impacts from BEVs allocate from manufacturing, operations and disposal.
Greenhouse gas emissions
The emission of greenhouse gas of BEVs come from all of its life cycle, but the intensity relies on two factors: size of the vehicle and fuel mix of the grid. The size of the vehicle will determine not only how much volume of raw materials is needed for the vehicle but also how big the battery needs to be as well as its disposal. The fuel mix, on the other hand, determines the emissions intensity of its operations. A grid with coal power could make an electric vehicle have a higher footprint than a small efficient ICE petroleum vehicle¹’²’³.
For simplicity purposes, the United States Department of Energy (DOE) estimates that the mean electric vehicle on the U.S. fuel mix electricity emits~1710 kg of carbon dioxide equivalent (CO2e) per year. While the precise numbers are different since most electric vehicles are located in States with lower than average emissions per kilowatt-hour, most of the electric vehicles worldwide are located in China, that relies heavily on coal. The average US grid resembles pretty much the share of low-carbon electricity of the world’s, which means that using DOE figure is a reasonable estimate. The grid intensity of the main markets of BEV, China that dominates with 53%, Europe 20%, USA 18% is ~850gCO2e/kWh, ~295 gCO2e/kWh, ~417 gCO2e/kWh respectively. According to the IEA, there were 4.8 million BEVs worldwide, which means that a lower-bound estimate for the operational emissions would be 8.2 million tons (Mt) CO2e .
Some analysis project higher share of low-carbon electricity by 2030 and beyond⁴’⁵, but others consider the possibility of different scenarios⁶’⁷, specially since China is adding new coal capacity and has historically failed to meet their emissions targets⁸. All in considered, since China’s current BEV have a median intensity more than 60% higher than that of the US, the DOE factor can be used for illustration purposes even if the carbon intensity of the grid worldwide declined. Under such scenario, the operation of 89.4 million BEVs globally would emit more than 150 Mt CO2e annually by 2030. Even if this is over-estimated by 50%, this would put BEVs on a level of emissions similar to countries like Belgium or Kuwait.
Next, the manufacturing of the car but especially the battery involves a high amount of emissions. Though several factors influence how carbon-intensive such process can be, the main driver is the size of the battery. The larger the battery, the larger the amount of resources and energy required, which then translates to different footprints based on the supply chain and energy source used. Based on the average across 12 studies⁹’¹⁰, manufacturing of the battery entails 134 kg CO2e/kWh. The average size of the battery vehicle sold now is 44 kwh, but the IEA expects is to gradually increase towards 70 to 80 kWh by 2030. Considering the midpoint between this range (75 kWh), the manufacturing of batteries for 89.4 million BEVs would imply 898.5 Mt CO2e in 2030, compared to 28.3 Mt CO2e of today’s assuming 44 kwh battery size. Using the lowest scenario in the studies for the carbon intensity but assuming the same upwards trend of battery size towards 75 kWh on average would lead to 201 Mt CO2e, lower though still significant. Consider that this can be allocated in the lifetime of the vehicle.
As for the manufacturing of the vehicle itself, which requires steel, plastic, aluminum, copper, glass, rubber and more, the mean kg CO2e per kWh is 213 across eight studies¹¹. For the 4.8 million BEVs with a mean size of 44 kWh of today’s levels, this leads to 45 Mt CO2e, while the 89.4 million BEVs by 2030 with a mean size of 75 kWh would mean 1,428 Mt CO2e emitted. This should also be allocated across the lifetime of the vehicle, i.e., this total level of emissions is to be expected over the decade when the stock of BEVs reaches 89.4 million. The disposal of the vehicle and its components including the battery accounts for roughly 5% of the total lifecycle emissions with close to 15 years of lifetime¹². This also ignores the required infrastructure to accommodate the BEVs, which has its peculiar challenges¹³’¹⁴’¹⁵.
Air pollution
The transportation sector in general is one of the drivers of atmospheric pollution. However, it has been getting better over time; several success stories have shown that it’s possible to leverage the power of technology to reduce the pollution coming out of the vehicle exhaust and improve air quality. The effects on health depends on the pollutant measured. However, not all pollutants come from the exhaust: particulate matter for example arises also from non-exhaust sources through brake, tire and road wear. Some studies have shown that non-exhaust particulate matter is higher than exhaust particulate matter¹⁵’¹⁶’¹⁷. Hence, even if the electric vehicles are charged during low-emissions periods of the grid, they still have a toll on pollution.
A 2018 study reviewed with detail 123 articles with different results in terms of life cycle atmospheric emissions of electric vehicles¹⁸. The results depend on the context: region analyzed, size of the vehicle, time of charging, driving conditions, fuel mix of electricity and infrastructure. Some studies, for instance, found that BEVs in China increase pollutants such as particulate matter (PM), sulfur oxides (SOx) and nitrous oxides(NOx). In other regions, generally NOx, carbon monoxide (CO), Volatile Organic Compounds (VOC), and ground ozone (O3) are reduced with BEVs, but SOx and PM increase relative to other vehicles. The main driver is the emissions profile of the grid; and as explained above, it is likely that over the next few years there won’t be significant improvements towards a cleaner grid, especially in the region with the fastest BEVs growth.
According to a 2019 study¹⁹, manufacturing of the 4.8 million batteries with a mean size of 44 kWh resulted in the emission of 10.1 Gg PM₁₀ eq. By 2030 with 89.4 million batteries with a mean size of 75 kWh, this would lead to 321 Gg PM₁₀ eq. For context, annual anthropogenic emissions of PM₁₀ are 62 537 Gg²⁰, of which 7% is attributable to the transportation sector. The non-exhaust emissions for BEVs²¹ can be calculated as 1.8 Gg for 2020, if we consider the average distance driven in China, but would rise to 35 Gg by 2030. This is another rough assumption since there is no hard data, but it’s for illustration purposes since a 2015 study found that the average China passenger car (with the largest BEV penetration) drives less than the average US vehicle, while both are higher than their European counterparts.
For SOx and NOx emissions from battery manufacturing, the 2019 study referenced above leads to 169 thousand metric tons (kt) of SOx and 20 kt of NOx in 2020, and 5,364 kt of SOx and by 650 kt of NOx by 2030. For reference, the OECD countries emit 8,788 kt of SOx and of 15,417 kt of NOx yearly²².The operational emissions for all pollutants described above depend on the grid, like in the case of GHG. Using the same assumption of the average US grid and hence the respective emission factors for SOx,NOx²³and PM₂.₅ ²⁴, and assuming the same distance driven in China with an average of 194 Wh/km, this leads to annually in 5.5 kt of SOx and NOx and 0.5 Gg of PM₂.₅ in 2020; and 104 kt of SOx and NOx and 9.5 Gg of PM₂.₅ annually by 2030. In order to have a proper comparison, we can refer to the image below¹⁸, where the panels compare different types of electric vehicles: top left (HEV), top right (PHEV), bottom left (BEV), and bottom right (FCEV). The scale displayed in these charts summarizes the findings of the 123 articles¹⁸, where 1 represents zero benefits in reducing emissions, 2 medium benefits, and 3 high benefits relative to petroleum cars.
Toxicity
The main concern with BEVs is the toxicity associated from the extraction and processing of raw materials needed to manufacture the vehicle and its disposal, especially for the battery. As an example, the batteries used in consumer electronics exceed on average the hazardous waste limits in California by more than 20-fold for Cobalt, 39-fold for Copper and 5-fold for Nickel²⁵. Consider that car batteries weight up to 10,000 more than a typical cellphone battery, and though they last longer and do not have exactly the same materials, they still comprise a severe threat to ecotoxicity and human health. A benchmark commonly used in Life Cycle Assesments is g 1,4-DCB eq. 1,4-Dichlorobenzene (para-Dichlorobenzene) is a regulated compound by the US EPA which categorizes it as Group C potential carcinogen²⁶. Several studies have shown that the impact of BEV in terms of both human toxicity and water toxicity using this parameter are two to three times larger relative to petroleum cars²⁷’²⁸’²⁹.
These studies, in addition to³⁰ state that the majority of the impact arises from mining and processing the raw materials needed. The IEA expects that cobalt demand expands to 180 kt per year by 2030, lithium to around 185 kt/year, manganese to 177 kt/year and nickel to 925 kt/year in order to have the 89.4 million BEVS. This would lead to the increase of toxic particles to human health and increased ecotoxicity due to arsenic, cadmium, cobalt, lead, mercury and manganese. The impacts of mining for these materials on the environment are well documented³¹’³²’³³’³⁴’³⁵, and the projected 10x–15x increase in demand for these metals is going to increase terrestrial and water ecotoxicity and is yet to be studied thoroughly.
The impact of the disposal of the vehicle and all its components, including the battery, can’t be disregarded either. The disposal of batteries in particular poses significant safety and environmental hazards in the waste management systems. The fluorinated components, organic solvents, nanoparticles, and leachable metals in their composition represent a large environmental risk and can lead to explosions or groundwater pollution. 65% of fire in waste facilities in California in 2017 were attributed to Lithium-ion batteries³⁶. Not only during their disposal but operational batteries at a large scale represent an explosion risk³⁷. Though the recycling of batteries is expected to increase by volume, it represents serious challenges to meet the requirements given the rate of growth³⁸’³⁹’⁴⁰. In the United States alone, the cumulative outflow in the waste stream of lithium ion cells could be up to 4 Mt by 2040⁴¹, almost a 900-fold increase of the annual volume of all batteries recollected in the country in 2012⁴².
Conclusion
Battery electric vehicles are lauded as the necessary technology to make transportation more sustainable when in fact they also have a significant toll on the environment. Cars changed the way people travel and live for better or worse, but ultimately have been instrumental for industrialized societies for they provide flexible , independent and long-ranged mobility. Their impact on quality of life and the environment is significant, but changing one type for the other won’t necessarily change this. While BEVs reduce noise and atmospheric pollution at the exhaust, their upstream and end-of-life impacts can offset these benefits even if the vehicles are charged with clean sources of electricity. Consumers and decision-makers should be informed that a BEV is not necessarily better for the environment, but rather come with tradeoffs like any technology. It is likely that the unintended consequences of this pushed technology increase the ecological impacts of the transportation sector.
